Heretofore, as one of the processes for molding a thermoplastic resin, there has been known a process for manufacturing a molding by placing a cylindrical body having a foamed layer (may be referred to as “foamed parison” hereinafter), which is formed by melt kneading together a resin and a blowing agent in an extruder and extruding the resulting melt from a die, in a mold and molding it.
For the above process for manufacturing a molding, general-purpose resins such as polyethylene resin, polypropylene resin and polystyrene resin have been studied.
Meanwhile, under such a situation that people's awareness of global environment is getting deeper and deeper and environmental problems such as the exhaustion of oil resources are now in the spotlight, polylactic acid resins derived from corn etc. are attracting attention in place of the above conventional general-purpose resins derived from oil resources. In expectation of the increasing general applicability of the polylactic acid resins in the future, the development of foams obtained from the polylactic acid resins is now under way.
However, as for polylactic acid resin foams, technologies related to foamed sheets are already disclosed by JP-A-2002-322309, JP-A-2002-3709, JP-A-2000-246259, etc. whereas the development of a polylactic acid resin molding obtained by placing a foamed parison of a polylactic acid resin in a mold is not under way.